The conformations, microdynamic behavior, and interactions with biologically important macromolecules, of the neurohypophyseal peptide hormones, of peptide hormone inhibitors (antagonists), of enkephalins, and of other biologically active peptides will be investigated. The relationships between biological activity and function and the dynamic and conformational behavior of the peptides will be sought. Specifically labeled (13C, 2H, 19F, etc.) amino acids, peptide hormones, and related analogs and derivatives will be prepared by total synthesis. High pressure liquid chromatography will be developed to preparatively purify these compounds to separate diastereoisomers. The interactions of the neurohypophyseal peptides with their carrier proteins will be examined using 13C nuclear magnetic resonance and other biophysical methods. The conformational and dynamic properties of peptide hormone inhibitors will be examined using nuclear magnetic resonance, circular dichroism, and lasar Raman spectroscopy, and the results will be compared with those from similar studies with the peptide agonists. These studies will be used to develop a physical-chemical basis for understanding the significance of the conformational and dynamic behavior of these peptides in various biological contexts.